Vehicle airbag system

ABSTRACT

A vehicle airbag system has an airbag which can be deployed in two stages. In a typical accident situation, a first chamber containing a larger quantity of propellant charge is deployed, and a second chamber containing a smaller quantity of propellant charge is deployed after a delay. If a particular accident situation is detected, such as the out-of-position situation or other person-specific and accident-specific variables, a deployment control device decides whether the ignition sequence is optimal, and reverses the sequence if applicable. The delay can also be varied on the basis of the detected variables.

BACKGROUND AND SUMMARY OF THE INVENTION

[0001] This application claims the priority of German Patent Document DE101 02 646.3, filed Jan. 20, 2001, the disclosure of which is expresslyincorporated by reference herein.

[0002] The invention relates to an airbag system for motor vehicles. Theairbag system has an airbag and a deployment arrangement, which fillsthe airbag with gas when an event occurs that can be interpreted as animpact against an obstacle. The deployment arrangement includes twoindependently-deployable chambers, each of which is capable of fillingthe airbag. The first chamber may fill the airbag more fully than thesecond chamber. After the first chamber has been deployed, the secondchamber is deployed with a time delay.

[0003] Airbag systems have become standard equipment for protectingmotor-vehicle passengers in accidents. An acceleration sensor providedon the vehicle frame usually detects whether an abrupt deceleration ofthe vehicle is to be interpreted as an impact against an obstacle. Insuch a case, a folded-up airbag is filled with gas in fractions of asecond through the deployment or ignition of a propellant charge inorder to catch the passenger's body and thus protect it againstsustained injuries.

[0004] Airbag systems of this type have performed well in practice.Vehicles of the upper-middle class, however, are already being providedwith dual-stage airbag systems, in which the deployment arrangementcomprises two chambers that contain an unequal distribution of therespective propellant charge. Conventionally, the propellant chamberwith the larger quantity of propellant charge (e.g., 70%) is deployedfirst. After a delay, the chamber having the correspondingly smallerquantity of propellant charge (e.g., 30%) is deployed. It is known tomake the time delay variable, notably as a function of the severity ofthe accident or crash as detected and assessed by appropriate sensors(EP 0 950 582 A2).

[0005] It has been seen that, for particular accident situations, theseconventional airbag systems cannot ensure the optimum protection of thepassengers in the involved vehicle. The passenger may be subjected tosignificant stress, especially a passenger in the so-called OOP(out-of-position) situation, in which his position differs from that ofan average or standard passenger. In the OOP situation, the passenger istypically too close to the airbag system, for example due to a brakingaction that has occurred prior to the crash or impact. Non-beltedchildren seated in the passenger seat are particularly at risk. They maybe located directly in the expansion space of the passenger airbag. Tooffer protection to those passengers in the OOP situation in the eventof an impact, it has already been proposed to place less propellantcharge in the first chamber than in the second chamber (DE 195 510980.A1, EP 0 958 974 A2). This, however, is a drawback for a passengerin the average or standard position.

[0006] In view of this, it is the object of the present invention todisclose an airbag system that functions optimally for the affectedpassenger in any accident situation.

[0007] The invention uses sensors to detect numerous person-specificvariables, especially accident-specific variables, such as the sittingposition, weight, size, the locked position of the safety belt, etc.Typical accident-specific variables include the actual vehicle speed andthe vehicle speed relative to a vehicle traveling in front of it, aswell as the nature of the crash.

[0008] With these sensors, it is possible to implement the reversibleignition sequence of the propellant charges of the two chambers inaccordance with the invention.

[0009] Other objects, advantages and novel features of the presentinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction with the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING

[0010]FIG. 1 is a schematic diagram showing the deployment arrangementof an airbag system of the present invention.

DETAILED DESCRIPTION OF THE DRAWING

[0011] The invention is described in detail below by way of theexemplary embodiment illustrated in the single drawing figure.

[0012]FIG. 1 schematically shows the deployment arrangement 2 of anairbag system 1. The airbag system 1 conventionally has a folded airbag,not shown, in a vehicle-side housing 3 indicated by dashed lines.Secured in the housing is a deployment unit 4, which contains twoseparate chambers 5 and 6 for a respective propellant charge. The firstchamber 5 can be deployed or ignited by way of a first ignition element7, and the second chamber 6 can be deployed by way of a second ignitionelement 8, independently of an ignition of the first chamber 5. Eachchamber 5, 6 has respective blowout openings 9 and 10.

[0013] A deployment control device 11 receives an acceleration signal 12from an acceleration sensor, not shown, that is mounted to the vehicleframe. The control device 11 compares this signal to a threshold valuestored inside the control device. If the threshold value is exceeded,the control device interprets the event that has effected thisacceleration signal 12 as an impact, which triggers a rapid filling ofthe airbag with gas through the ignition of the propellant charges inthe chambers 5 and 6. The threshold value is selected such that theairbag is not filled if emergency braking occurs.

[0014] In the illustrated case, the deployment control device 11transmits a first ignition signal to the ignition element associatedwith the chamber containing the larger quantity of propellant charge.They are the first ignition element 7 and first chamber 5, respectively.Then, after a delay the control device 11 transmits an ignition signalto the second ignition element 8 for the smaller quantity of propellantcharge in the second chamber 6. Consequently, the airbag is filled intwo stages: first with the larger quantity of gas, then with the smallerquantity of gas in the end phase. A bus system 13 schematicallyrepresents the transmission of the ignition signals to the ignitionelements 7 and 8. Dashed lines 14 show that further restraining systemssuch as belt tighteners, side airbags and the like can also be actuatedin the same manner by the deployment control device 11 in theillustrated scenario.

[0015] The vehicle contains further sensors (not shown in detail) thatdetect variables associated with the passenger or the seats. One of suchvariables, for example, is the seat setting that is indicative of thesitting position and therefore the type of person. In other words, theydetect whether the passenger is large or small. The sensors furtherdetect a weight signal, i.e., whether the person is heavy orlightweight, and particularly whether a person is occupying the seat,and other such person-specific variables. A corresponding signal 15 isessentially transmitted to the deployment control device 11.

[0016] It is also advantageous to detect accident-specific variables.For example, the deployment control device 11 can be supplied with asignal 16 that indicates the crash angle, that is, the direction of theprimary component of the force acting in an impact. This directiondeviates from a specified axis, generally the longitudinal axis of thevehicle. It is further advantageous to detect the actual speed of thevehicle, the vehicle speed relative to an object located in front of thevehicle, typically another vehicle traveling ahead of the vehicle, andto transmit corresponding signals to the deployment control device 11.The deployment control device 11 is also supplied with specificvariables relating to the vehicle type, or it permanently stores thesevariables, as indicated by a type signal 17. The accident-specific andperson-specific variables supplied to the deployment control device 11are evaluated in terms of the vehicle type in the deployment controldevice 11. Based on this evaluation, it is not only possible to select avariable time delay between the ignition of the two ignition elements 7and 8, as is already known per se, but it can also be determined whethera particular accident situation is occurring in which it would be morepractical to deploy the airbag containing the smaller quantity of gasfirst, then fill it with the larger quantity of gas following a delay.In the illustrated case, the corresponding signals are transmitted tothe ignition elements 7 and 8 in reverse order, so the propellant chargein the second chamber 6 is ignited first. The larger quantity ofpropellant charge in the first chamber 5 is ignited after acorresponding delay.

[0017] The variable ignition sequence for the chambers 5 and 6 of thedual-stage deployment unit 4 allows the stress values of the passenger,which are adapted to the respective accident situation, to be reduced tomore favorable values. This is especially crucial for the OOP situation.Furthermore, there are more possible degrees of freedom in optimizingthe deployment of the airbag, notably with respect to an adaptation toany accident situations that may arise.

[0018] As of the year 2003, the FMVSS 208 regulation will stipulatetests for the OOP situation for the driver and passenger sides,especially for US vehicles.

[0019] The foregoing disclosure has been set forth merely to illustratethe invention and is not intended to be limiting. Since modifications ofthe disclosed embodiments incorporating the spirit and substance of theinvention may occur to persons skilled in the art, the invention shouldbe construed to include everything within the scope of the appendedclaims and equivalents thereof.

What is claimed:
 1. An airbag system for a vehicle having sensors thatdetect at least one of an accident-specific variable and aperson-specific variable, the system comprising: an airbag; a deploymentarrangement adapted to fill the airbag with gas when the deploymentarrangement interprets an event as an impact against an obstacle, thedeployment arrangement including: independently deployable first andsecond chambers, the first chamber being capable of filling the airbagwith a larger quantity of gas than the second chamber, wherein thedeployment arrangement is configured to determine whether to deploy thefirst or second chamber first on the basis of an evaluation of the atleast one of an accident-specific variable and a person-specificvariable.
 2. The airbag system according to claim 1, wherein the sensorsinclude sensors for detecting at least one of an actual vehicle speedand a relative vehicle speed, and wherein the deployment arrangement isconfigured to determine whether to deploy the first or second chamberfirst on the basis of an evaluation of at least one of an crash angleand a crash severity, each of the crash angle and crash severity beingdetermined as a function of at least one of vehicle type, the actualvehicle speed and the relative vehicle speed.
 3. The airbag systemaccording to claim 2, wherein the sensors include sensors for detectinga body size, a body weight, a sitting position and an out-of-positionsignal, and wherein the at least one of an accident-specific variableand a person-specific variable includes a person type determined as afunction of the body size, the body weight, the sitting position and theout-of-position signal.
 4. The airbag system according to claim 1,wherein the sensors include sensors for detecting a body size, a bodyweight, a sitting position and an out-of-position signal, and whereinthe person-specific variable includes a person type determined as afunction of the body size, the body weight, the sitting position and theout-of-position signal.
 5. The airbag system according to claim 4,wherein a delay between the deployment of the first and second chambersis determined on the basis of severity and nature of a crash.
 6. Theairbag system according to claim 3, wherein a delay between thedeployment of the first and second chambers is determined on the basisof severity and nature of a crash.
 7. The airbag system according toclaim 2, wherein a delay between the deployment of the first and secondchambers is determined on the basis of severity and nature of a crash.8. The airbag system according to claim 1, wherein a delay between thedeployment of the first and second chambers is determined on the basisof severity and nature of a crash.
 9. A method for deploying an airbagsystem for a vehicle having sensors that detect at least one of anaccident-specific variable and a person-specific variable, the airbagsystem including airbag and a deployment arrangement adapted to fill theairbag with gas when the deployment arrangement interprets an event asan impact against an obstacle, the deployment arrangement includingindependently deployable first and second chambers, the first chamberbeing capable of filling the airbag with a larger quantity of gas thanthe second chamber, the method comprising: evaluating the at least oneof an accident-specific variable and a person-specific variable;determining whether to deploy the first or second chamber first usingthe at least one of an accident-specific variable and a person-specificvariable; and deploying the first and second chambers in the determinedsequence to fill the airbag with gas when the deployment arrangementinterprets an event as an impact against an obstacle.
 10. The methodaccording to claim 9 further comprising detecting at least one of anactual vehicle speed and a relative vehicle speed using at least one ofthe sensors, and wherein evaluating the at least one of anaccident-specific variable and a person-specific variable includesevaluating at least one of an crash angle and a crash severity as afunction of at least one of vehicle type, the actual vehicle speed andthe relative vehicle speed.
 11. The method according to claim 9 furthercomprising detecting a body size, a body weight, a sitting position andan out-of-position signal using at least one of the sensors, and whereinevaluating the at least one of an accident-specific variable and aperson-specific variable includes evaluating a person type as a functionof the body size, the body weight, the sitting position and theout-of-position signal.
 12. The method according to claim 9 furthercomprising determining a delay between the deployment of the first andsecond chambers on the basis of severity and nature of a crash.